The automated detection and measurement of substances in solution has long been determined by a variety of known techniques which may be generally classified as either batch or flow analysis. In order that the advantages and novel aspects of the present invention be clearly understood, the essential features and limitations of the methods and means of the prior art will now be briefly described. A review of the field related to electrochemical analysis is provided by Feher, Zs; Nagy, G; Toth, K; Pungor, E. in CRC Crit. Rev. Anal. Chem. 1983. 14, 175-230 (hereinafter "Feher et al"). Descriptions of the prior art may also be found in standard textbooks such as "Instrumental Methods of Analysis", Sixth Edition, by Willard, Merritt, Dean and Settle, Wadworth Publishing Company, 1981.